The purpose of the present proposal is to study the role of temporal and perceptual similarity factors in the infant's organization of his/her speech discrimination of sounds in multisyllabic utterances. Experiment I studies the infant's ability to recognize a previously learned monosyllabic contrast when embedded in different temporal locations in two other syllables that are perceptually identical to each other or very different. Experiment II studies the infant's ability to learn to discriminate a bisyllabic contrast that is presented in the context of one of several familiar monosyllables. The monosyllables occur in either the initial, medial, or final position in these utterance strings. It is anticipated that the results of these experiments, taken together with those of their respective follow-up studies, will offer us important information about the constraints that operate in the use of the infant's impressive speech perception abilities in learning to recognize new sounds and words in his/her early stages of language development.